The present invention relates to a device manufacturing-related apparatus, gas purge method, and device manufacturing method and, more particularly, to a device manufacturing-related apparatus (e.g., an exposure apparatus, gas purge apparatus, reticle inspection apparatus, or reticle transfer box) having a space for storing a reticle with a pellicle whose pellicle film is supported by a pellicle frame, a gas purge method of purging the pellicle space within the pellicle frame with inert gas, and a device manufacturing method.
A manufacturing process for a semiconductor element such as an LSI or VLSI formed from a micropattern uses a reduction type projection exposure apparatus for printing and forming by reduction projection a circuit pattern drawn on a mask onto a substrate coated with a photosensitive agent. With an increase in the packaging density of semiconductor elements, demands have arisen for further micropatterning. Exposure apparatuses are coping with micropatterning along with the development of a resist process.
Methods of increasing the resolving power of the exposure apparatus include a method of changing the exposure wavelength to a shorter one, and a method of increasing the numerical aperture (NA) of the projection optical system.
As for the exposure wavelength, a KrF excimer laser with an oscillation wavelength of 365-nm i-line to recently 248 nm, and an ArF excimer laser with an oscillation wavelength around 193 nm have been developed. A fluorine (F2) excimer laser with an oscillation wavelength around 157 nm is also under development.
An ArF excimer laser with an oscillation wavelength around ultraviolet rays, particularly, 193 nm, and a fluorine (F2) excimer laser with an oscillation wavelength around 157 nm are known to have an oxygen (O2) absorption band around their wavelength band.
For example, a fluorine excimer laser has been applied to an exposure apparatus because of a short oscillation wavelength of 157 nm. The 157-nm wavelength falls within a wavelength region called a vacuum ultraviolet region. In this wavelength region, light is greatly absorbed by oxygen molecules, and hardly passes through the air. The fluorine excimer laser can only be applied in an environment in which the pressure is decreased to almost vacuum and the oxygen concentration is fully decreased. According to reference xe2x80x9cPhotochemistry of Small Moleculesxe2x80x9d (Hideo Okabe, A Wiley-Interscience Publication, 1978, p. 178), the absorption coefficient of oxygen to 157-nm light is about 190 atmxe2x88x921cmxe2x88x921. This means when 157-nm light passes through gas at an oxygen concentration of 1% at one atmospheric pressure, the transmittance per cm is only
T=exp(xe2x88x92190xc3x971 cmxc3x970.01 atm)=0.150
Oxygen absorbs light to generate ozone (O3), and ozone promotes absorption of light, greatly decreasing the transmittance. In addition, various products generated by ozone are deposited on the surface of an optical element, decreasing the efficiency of the optical system.
To prevent this, the oxygen concentration in the optical path is suppressed to low level of several ppm order or less by a purge means using inert gas such as nitrogen in the optical path of the exposure optical system of a projection exposure apparatus using a far ultraviolet laser such as an ArF excimer laser or fluorine (F2) excimer laser as a light source.
In such an exposure apparatus using an ArF excimer laser with a wavelength around ultraviolet rays, particularly, 193 nm, or a fluorine (F2) excimer laser with a wavelength around 157 nm, an ArF excimer laser beam or fluorine (F2) excimer laser beam is readily absorbed by a substance. The optical path must be purged to several ppm order or less. This also applies to moisture, which must be removed to ppm order or less.
For this reason, the interior of the exposure apparatus, particularly, the optical path of ultraviolet rays is purged with inert gas. A load-lock mechanism is arranged at a coupling portion between the inside and outside of the exposure apparatus. When a reticle or wafer is to be externally loaded, the interior of the exposure apparatus is temporarily shielded from outside air. After the load-lock mechanism is purged of oxygen or water with inert gas, the reticle or wafer is loaded into the exposure apparatus.
FIG. 1 is a sectional view schematically showing an example of a semiconductor exposure apparatus having a fluorine (F2) excimer laser as a light source and a load-lock mechanism.
In FIG. 1, reference numeral 1 denotes a reticle stage for setting a reticle bearing a pattern; 2, a projection optical system for projecting the pattern on the reticle onto a wafer; 3, a wafer stage which supports the wafer and is driven in the X, Y, Z, xcex8, and tilt directions; 4, an illumination optical system for illuminating the reticle with illumination light; 5, a guide optical system for guiding light from the light source to the illumination optical system 4; 6, a fluorine (F2) laser serving as a light source; 7, a masking blade for shielding exposure light so as not to illuminate the reticle except the pattern region; 8 and 9, housings which cover the exposure optical path around the reticle stage 1 and wafer stage 3, respectively; 10, an He air-conditioner for adjusting the interiors of the projection optical system 2 and illumination optical system 4 to a predetermined He atmosphere; 11 and 12, N2 air-conditioners for adjusting the interiors of the housings 8 and 9 to a predetermined N2 atmosphere; 13 and 14, reticle load-lock chambers and wafer load-lock chambers used to load a reticle and wafer into the housings 8 and 9, respectively; 15 and 16, a reticle hand and wafer hand for transferring the reticle and wafer, respectively; 17, a reticle alignment portion used to adjust the reticle position; 18, a reticle stocker for stocking a plurality of reticles in the housing 8; and 19, a pre-alignment unit for pre-aligning the wafer.
If necessary, the overall apparatus is stored in an environment chamber (not shown). Air controlled to a predetermined temperature is circulated within the environment chamber to keep the internal temperature of the chamber constant.
FIG. 2 is a schematic sectional view showing another example of the semiconductor exposure apparatus having a fluorine (F2) excimer laser as a light source and a load-lock mechanism.
The whole exposure apparatus shown in FIG. 2 is covered with a housing 20, and the interior of the housing 20 is purged of O2 and H2O with N2 gas. Reference numeral 21 denotes an air-conditioner for setting the entire housing 20 in an N2 atmosphere. In this exposure apparatus, the internal spaces of a lens barrel 2 and illumination optical system 4 are partitioned from the internal space (driving system space) of the housing 20, and independently adjusted to an He atmosphere. Reference numerals 13 and 14 denote a reticle load-lock chamber and wafer load-lock chamber used to load a reticle and wafer into the housing 20, respectively.
In general, a reticle is equipped with a pattern protection device called a pellicle. The pellicle prevents deposition of a foreign matter onto a reticle pattern surface, and suppresses the occurrence of defects caused by transfer of a foreign matter onto a wafer.
FIG. 3 is a schematic view showing the structure of a reticle with a pellicle. A pellicle 24 is adhered to the pattern surface of a reticle 23 with an adhesive agent or the like. The pellicle 24 is made up of a pellicle support frame (pellicle frame) 25 large enough to surround the reticle pattern, and a pellicle film 26 which is adhered to one end face of the pellicle support frame 25 and transmits exposure light. If a space (to be referred to as a pellicle space hereinafter) defined by the pellicle 24 and reticle 23 is completely closed, the pellicle film 26 may expand or contract due to the difference in atmospheric pressure between the inside and outside of the pellicle space or the difference in oxygen concentration. To prevent this, a vent hole 27 is formed in the support frame 25 so as to allow gas to flow between the inside and outside of the pellicle space. An auto-screen filter (not shown) is attached to the ventilation path in order to prevent an external foreign matter from entering the pellicle space via the vent hole 27.
FIG. 4 is a schematic view showing an example of a reticle transfer path in the exposure apparatus shown in FIGS. 1 and 2. In FIG. 4, reference numeral 22 denotes a foreign matter inspection device which measures the size and number of foreign matters such as dust deposited on a reticle surface or pellicle film surface. The reticle 23 is loaded manually or by a transfer device (not shown) into the reticle load-lock chamber 13 serving as the entrance of the exposure apparatus. Since the reticle and pellicle are generally adhered outside the exposure apparatus, the pellicle 24 has already been adhered to the loaded reticle 23. The interior of the reticle load-lock chamber 13 is purged with inert gas until the interior reaches an inert gas atmosphere similarly to the housing 8. After that, the reticle 23 is transferred by the reticle hand 15 to any one of the reticle stage 1, reticle stocker 18, and foreign matter inspection device 22.
As described above, an exposure apparatus using ultraviolet rays, particularly, an ArF excimer laser beam or fluorine (F2) excimer laser beam suffers large absorption of the ArF excimer laser beam or fluorine (F2) excimer laser of its wavelength by oxygen and moisture. To obtain a sufficient transmittance and stability of ultraviolet rays, the oxygen and moisture concentrations must be reduced and controlled strictly. For this purpose, a load-lock mechanism is arranged at a coupling portion between the inside and outside of the exposure apparatus. When a reticle or wafer is to be externally loaded into the exposure apparatus, the reticle or wafer is temporarily shielded from outside air. After the interior of the load-lock mechanism is purged of gas such as oxygen with inert gas, the reticle or wafer is loaded into the exposure apparatus.
A reticle loaded into the load-lock chamber bears a pellicle, and the pellicle space can communicate with outside air only through a relatively small vent hole. This structure prolongs a time required to complete purge in the pellicle space even after the interior of the reticle load-lock chamber reaches a predetermined inert gas concentration, degrading the productivity.
As for the vent hole of the pellicle frame, Japanese Patent Laid-Open Nos. 6-27643 and 9-197652 disclose inventions of forming intake and exhaust holes in a pellicle frame. Even if the number of holes or the hole area is increased, the diffusion phenomenon caused by the difference in inert gas concentration between the inside and outside of the pellicle space merely contributes to the purge mechanism as long as the pellicle is set in an inert gas atmosphere. The pellicle space requires a longer purge time, compared to the load-lock chamber which is forcibly purged. When a valve or auto-screen filter is arranged in the hole path, the purge time is further prolonged.
Japanese Patent Laid-Open No. 9-73167 discloses an invention of adhering a reticle and pellicle in advance in an inert gas atmosphere and filling the pellicle space with inert gas at an oxygen concentration of 1% or less. However, the transmittance of 157-nm light is merely 15% per cm in atmospheric-pressure gas at an oxygen concentration of 1%. At present, the gap between the reticle and the pellicle is about 6 mm. Even if this gap is filled with gas at an oxygen concentration of 0.1%, the transmittance of 157-nm light at the gap is merely 89.2%. The total space distance of an optical path from the light source of the exposure apparatus to a wafer exceeds at least 1 m. To ensure a transmittance of 80% or more in the 1-m space, the oxygen concentration must be suppressed to 10 ppmv/v or less, and ideally 1 ppm or less. In the pellicle space, the oxygen concentration must be 1 to 100 ppm or less in terms of the balance with another space and maintenance of the transmittance in the total space distance. This also applies to the moisture and carbon dioxide gas concentrations.
The pellicle space may be temporarily filled with inert gas at these ppm-order oxygen concentrations. If, however, the oxygen concentration of a space where the reticle and pellicle are set is higher than the internal oxygen concentration, oxygen enters the pellicle space via a small gap because the adhering surface between the pellicle frame and the reticle is not a completely airtight structure. The oxygen concentration can be maintained in % order, but it is very difficult to maintain the oxygen concentration in ppm order. A pellicle film made of a fluorine-based resin has oxygen permeability, and it is more difficult to maintain the oxygen concentration in ppm order. A reticle may be set on the reticle stage and exposed at an unsatisfactory inert gas concentration in the pellicle space. Since the inert gas concentration in the pellicle space gradually comes close to an ambient inert gas concentration on the reticle stage, the transmittance of exposure light in the pellicle space changes. As a result, a predetermined exposure amount cannot be stably obtained on a wafer, and an error such as a change in transfer pattern size may occur.
A reticle with a pellicle that is stocked in air outside the exposure apparatus often bears many water molecules deposited on the surface including the pellicle film and pellicle frame. Also when the reticle is stocked in an inert gas atmosphere, the reticle may be exposed to the outside air during loading into the exposure apparatus, and the same problem may occur.
The amount of water molecules deposited on the surface of the pellicle film or the like greatly depends on the microscopic roughness of the surface, the surface shape, and particularly whether the surface is hydrophilic or hydrophobic. For a resin material, the resin may slightly absorb water. It is not rare to use a fluorine-based resin material for the pellicle film or auto-screen filter. A large amount of water may be deposited on or in the surface or absorbed in it.
In this case, even if the pellicle space is purged with inert gas, water molecules deposited on the surface or absorbed in it are gradually eliminated into inert gas. It is very difficult to decrease the water concentration in the pellicle space to ppm order within a short time. The water concentration during the purge period can be decreased by increasing the inert gas supply flow rate. Even when purge stops, water elimination continues to gradually increase the water concentration in the narrow pellicle space.
Exposure of a pattern using such a reticle gradually changes the transmittance for exposure light. As a result, a predetermined exposure amount cannot be stably obtained on a wafer, and the size of a pattern transferred to the wafer changes.
To solve this problem, a vent hole may be formed in the reticle frame to forcibly supply inert gas into the pellicle space via the vent hole. In this method, a reticle with a pellicle is aligned at a predetermined position. Assuming that the pellicle frame exists at a predetermined position, an inert gas supply portion is moved close to the pellicle frame. If, however, the pellicle frame shifts from the predetermined position, excessive force is applied to the pellicle frame to deform it.
The present invention has been made in consideration of the above situation, and has as its object to solve problems caused by misalignment of a pellicle frame at an improper position and to minimize deformation of the pellicle frame when an inert gas supply portion is moved close to the pellicle frame to supply inert gas into the pellicle space.
According to the first aspect of the present invention, there is provided a device manufacturing-related apparatus having a space for storing a reticle with a pellicle whose pellicle film is supported by a pellicle frame, comprising an alignment mechanism which aligns the pellicle frame at a predetermined position.
According to a preferred aspect of the present invention, it is preferable that the reticle with the pellicle have a vent hole in the pellicle frame, and the device manufacturing-related apparatus further comprise an inert gas supply portion which supplies inert gas via the vent hole into a pellicle space serving as a space within the pellicle frame.
According to another preferred aspect of the present invention, the alignment mechanism preferably aligns-the pellicle frame by moving the inert gas supply portion. Alternatively, the alignment mechanism preferably aligns the pellicle frame by using the inert gas supply portion as an alignment reference.
According to still another preferred aspect of the present invention, it is preferable that a distal end of the inert gas supply portion comprise an elastic member, and the alignment mechanism bring the elastic member and the pellicle frame into tight contact with each other in alignment and supplying inert gas. A width of the elastic member in a direction perpendicular to a surface of the pellicle film is preferably substantially equal to a width of the pellicle frame in the direction perpendicular to the surface of the pellicle film.
According to still another preferred aspect of the present invention, the alignment mechanism preferably presses the pellicle frame by a distal end of the inert gas supply portion in alignment and supplying inert gas. The alignment mechanism preferably comprises a sensor which detects force applied to the pellicle frame, and controls, based on an output from the sensor, force for pressing the pellicle frame by the distal end of the inert gas supply portion. The alignment mechanism preferably presses the pellicle frame by the distal end of the inert gas supply portion in a direction parallel to a surface of the pellicle film.
According to still another preferred aspect of the present invention, it is preferable that the reticle with the pellicle have first and second vent holes in the pellicle frame, and the device manufacturing-related apparatus further comprise an inert gas supply portion which supplies inert gas via the first vent hole into a pellicle space serving as a space within the pellicle frame, and an inert gas exhaust portion which exhausts gas in the pellicle space via the second vent hole.
According to still another preferred aspect of the present invention, the alignment mechanism preferably aligns the pellicle frame by moving at least one of the inert gas supply portion and the inert gas exhaust portion. Alternatively, the alignment mechanism preferably aligns the pellicle frame by using either of the inert gas supply portion and the inert gas exhaust portion as an alignment reference. Alternatively, the alignment mechanism preferably aligns the pellicle frame by driving at least one of the inert gas supply portion and the inert gas exhaust portion so as to sandwich the pellicle frame by the inert gas supply portion and the inert gas exhaust portion.
According to still another preferred aspect of the present invention, the alignment mechanism preferably comprises a sensor which detects force applied to the pellicle frame, and controls driving of at least one of the inert gas supply portion and the inert gas exhaust portion on the basis of an output from the sensor.
According to still another preferred aspect of the present invention, the alignment mechanism preferably drives at least one of the inert gas supply portion and the inert gas exhaust portion in a direction parallel to a surface of the pellicle film.
According to still another preferred aspect of the present invention, at least one of the inert gas supply portion and the inert gas exhaust portion is preferably supported pivotally about a shaft perpendicular to a surface of the pellicle film.
According to still another preferred aspect of the present invention, it is preferable that the device manufacturing-related apparatus further comprise a sensor which detects a position of the pellicle frame, and the alignment mechanism align the pellicle frame at the predetermined position on the basis of an output from the sensor.
According to still another preferred aspect of the present invention, the device manufacturing-related apparatus preferably further comprises an exposure section which exposes a substrate with a pattern formed on the reticle.
The device manufacturing-related apparatus can be constituted as an exposure apparatus which exposes a substrate to a pattern formed on the reticle, a gas purge apparatus which purges, with inert gas, gas in the pellicle space serving as a space within the pellicle frame, a reticle stocker which stocks the reticle, a reticle inspection apparatus which inspects the reticle, or a reticle transfer box for transferring the reticle.
According to the second aspect of the present invention, there is provided a gas purge method of purging, with inert gas via a vent hole formed in a pellicle frame, gas in a pellicle space serving as a space within the pellicle frame of a reticle with a pellicle whose pellicle film is supported by the pellicle frame, comprising the steps of aligning the pellicle frame at a predetermined position, and supplying inert gas from an inert gas supply portion into the pellicle space via the vent hole while the inert gas supply portion is in tight contact with the pellicle frame.
According to the third aspect of the present invention, a device is manufactured by using the above-described device manufacturing-related apparatus.
According to the fourth aspect of the present invention, there is provided a device manufacturing method of manufacturing a device through a lithography process, wherein in the lithography process, a pattern is transferred onto a substrate by using the device manufacturing-related apparatus serving as an exposure apparatus.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.